The present invention relates to converter circuits and more particularly to pre-bias protection circuits for the converter circuits.
Voltage, pre-existing at an output stage of a converter, for example, a converter circuit 8 having a transistor stage 10 illustrated in FIG. 1, prior to start up is referred to as pre-bias voltage. When the converter circuit 8 starts up, high- and low-side switches 12 and 14 of the transistor stage 10 will be driven by high- and low-side switch control signals Hdrv and Ldrv from respective high- and low-side gate drivers. When the low-side switch control signal Ldrv is applied to the low-side switch 14 during startup, the output capacitor C0 having the pre-bias voltage may discharge through the output inductor L and the low-side switch 14. Discharging the pre-bias voltage may result in glitches and cause problems in systems, e.g., multi-processor systems.
In order not to discharge the pre-bias voltage, specific attention needs to be taken during a start up of the converter circuit 8. Therefore, because discharge of the pre-bias voltage is undesirable, discharging of the output capacitor C0 of the converter circuit 8 should be prevented and reversal of an inductor current must not be allowed.